Test times out unexpectedly, despite expected behavior otherwise

Hi there, @clavery63 and I have noticed some behavior that we believe is a bug, resulting in tests timing out when they should complete successfully.

I’ve reproduced here https://codesandbox.io/s/suspicious-ardinghelli-0yt2n

import { cold } from "jest-marbles";

describe("timeout error", () => {
  test("times out without completing observable", done => {
    const fakeActions = cold("t|", { t: true });

    fakeActions.subscribe({
      next: value => {
        console.log("value received:", value);
        expect(value).toEqual(true);
      },
      complete: () => {
        console.log("observable complete");
        done();
      }
    });
  });
});

Based on the way the logs appear, and our understanding of the tools involved, we’d expect the test to pass, but instead it times out.

If this is expected behavior, please let us know if you have thoughts on how to go about testing this sort of thing effectively. Thanks!

[just-jeb]

Please use toSatisfyOnFlush, available since 2.5.0.
Let me know if that helps.

[just-jeb]

Yeah, it seems that testing side effects is currently a bit problematic. I have a few things in mind (such as adding toHaveSideEffect matcher), will see what can be done.
There is a workaround for you until it’s done though. You can pipe to the tested stream and tap your assert:

    const mapStreamWith = (mapper: any) => (stream: any) => stream.pipe(map(mapper));
        const fakeStream = cold("t|");
    const mapSpy = jest.fn().mockReturnValue('r');
    const streamMapper = mapStreamWith(mapSpy);
    const testee = streamMapper(fakeStream).pipe(tap(() => {
      expect(mapSpy.mock.calls.length).toEqual(1);
    }))
    expect(testee).toBeMarble('r|');